Question: Solve for $z$ : $-19 = z - 30$
Explanation: Add $30$ to both sides: $ \begin{eqnarray} \\ \hphantom{-19 {+ 30}} &\hphantom{=}& \hphantom{z} \\ -19 &=& z - 30 \\ \\ {+30} && {+30} \\ \end{eqnarray} $ $ \begin{eqnarray} \\ -19 {+ 30} &=& z \\ \end{eqnarray} $ Simplify. $ z = 11$